Perhaps never before has so much attention been paid to groups of students once largely overlooked. Minority students, students in special education classes, students with limited English skills, chronic truants - the requirements of the No Child Left Behind federal education law today make it much harder for schools to ignore their particular needs. The good news is that school reforms are shining a new light on needs like theirs. The bad news is that too few schools are able to deal effectively with them. Over the next three weeks we will take a look at some of the children on the margins. We'll examine some hopeful solutions emerging to counter the problems they face - and measure the considerable ground still to be covered before our schools will truly be able to boast that they are leaving no children behind.

Homelessness can't put up many barriers to education that the Thomas J. Pappas School hasn't anticipated. The buses for its three campuses in Phoenix and Tempe change routes as often as students change locations - daily.

At the elementary school in Phoenix - the flagship campus - the clothing room is nicknamed The Gap. Students can "shop" here once a month (or anytime they're in need) for new underwear and socks, gently worn clothes, and warm blankets. Down the hall there's a clinic, for everything from a morning shower to a visit to the dentist. And just off the cafeteria there are two special rooms: one filled with donated toys and stuffed animals, where children pick a gift for their birthday; the other stocked with food to take in the evening.

"I move around a lot, that's kind of why I come here," says Danielle Bradshaw, a sprightly sixth-grader at the middle school. "Every time we move we end up losing our stuff, so I come here and they help me get different stuff."

When a tutoring program outgrew its space at a homeless shelter, Sandra Dowling, the Maricopa County school superintendent, started the Pappas School in 1990. It now serves about 1,000 students and is raising money to build a new facility for grades 7 through 12. Some children come to the school year after year, but officials say most stay just a few months, until they transition into another local school or move out of the region.

Pappas is a place where the needs of homeless children come into sharp focus. And the ranks of these children appear to be growing. The US Conference of Mayors surveyed 27 cities, for instance, and found that requests for emergency shelter for families with children were up about 7 percent last year. Such families make up 40 percent of the cities' homeless populations.

But visiting educators who come to see Pappas in action have to find a way to apply its practices in regular public schools; starting schools solely for homeless children is no longer allowed under federal law.

In the 1990s, the US had at least 40 such schools, many of them housed in shelters. Districts sometimes required families in shelters to enroll their children in the on-site schools. But advocates for homeless students charged that these programs were separate and unequal.

"The vast majority didn't provide the same level of education or extracurriculars," says Barbara Duffield, policy director of the National Association for the Education of Homeless Children and Youth (NAEHCY) in Minneapolis. "The public schools, rather than taking [children] in and removing barriers, were creating dumping grounds."

The Pappas School was considered better than the bulk of these separate programs, but its academic quality was questioned as well. In testimony before a congressional committee in 2000, Luisa Stark, chair of the Phoenix Consortium to End Homelessness, criticized Pappas for low test scores, compared with those of homeless students integrated into other Arizona schools.

In 2002, requirements for integration were strengthened under a law known as McKinney-Vento. Ms. Dowling and her supporters had gone to bat for Pappas, however. Her school and similar ones in three California counties were grandfathered in under provisions introduced by their representatives in Congress.

The law insists that they meet the same standards as other public schools, and that they notify families of the right to enroll students in regular schools.

Recent data from the state Department of Education show that Pappas students generally outperform homeless students in integrated schools on the reading portion of AIMS (Arizona's Instrument to Measure Standards). In third grade, for instance, 53 percent of Pappas students met or exceeded the standards, compared with 39 percent of homeless students in the 21 districts that received McKinney-Vento grants. In math, however, the scores were lower at Pappas in three of four grade levels tested.

Many families choose Pappas because word gets around about the love and acceptance students feel here, Dowling says. "You take those kids that are extremely high risk ... that everyone in society has written off, and you say to those kids, 'You're important, and I'm going to make sure that you know how important you are.' "

Indeed, the only thing visibly different about the diverse students here is how much they hug. At every step, staff, volunteers, and fellow students are liable to find themselves wrapped in an earnest embrace.

Danielle's explanation for the hugs she gives to classmates: "We're all just friends.... At regular schools, there's always a fight, but we don't do that much here because we're more focused on what we need than what we want."

Social worker Erin Angelini spent so much time with Pappas families that she set up an office at the elementary school. "A lot of the kids I work with have conduct disorders - emotional problems they're just not coping with," she says.

A nonprofit group also runs play-therapy sessions in a special room here, observing children as they use toys to act out troubling situations.

Kay Ercius, who pairs up volunteer mentors and children, tells of a girl who was selectively mute - she would speak at home, but not at school or to strangers. Ms. Ercius matched her with a talkative woman, and after about a year, she got an unforgettable e-mail: "It said, 'Ashley read out loud to me in the library today,' " she says with teary eyes.

The physical needs are often easier to detect than the emotional ones. Eileen Smith, the head nurse, says many of the health problems are related to overcrowded living situations.

Around the corner, dentist Tim Bashara is peering into Yhazmein's mouth, asking about her favorite cartoon. " 'The Simpsons,' " she replies. When he asks her if he looks like Homer, she laughs. "No, he's chunky!"

Dental problems can be severe. Instead of cereal or fruit, some of the kids eat "hot cheese doodles for breakfast," Ms. Smith says. Many students have never been to a dentist before.

Working with homeless children "rocks your world sometimes," says Ernalee Phelps, director of public relations and resource development at Pappas.

Ms. Phelps knows children who are staying in dilapidated houses with no locks, and they tell her about drug dealers or the prostitute who got pregnant. "You don't know when you come to work what emotion you're going to trigger," she says.

Phelps also sees cases of chronic homelessness: A few former students now have children of their own attending Pappas. But there's also a lot of joy - "the marvel of the success of our kids," she says. A scholarship from Pappas has helped a number of alumni go to college.

"I'm sure there are good practices that separate schools have developed because of the intensive interaction they've had," says Patricia Popp, NAEHCY president. "The goal would be that we ... make it part of the norm in all schools, [so fewer people think] a separate school is necessary."